Process for generating high-pressure fuel and system for generating high fuel pressure

Abstract

A process and system for generating and delivering high-pressure fuel to a high-pressure storage chamber of a fuel injection system of an internal combustion engine. The system includes a low-pressure pump as a pre-feed pump by which fuel is supplied from a tank and is delivered to the intake side of a high-pressure pump and a part of the fuel delivered by the low-pressure pump is used to lubricate the high-pressure pump. In order to reduce the temperature level in the return and to increase the overall efficiency of the motor, the system is embodied so that the delivery quantity of the low-pressure pump or the delivery pressure on the delivery side of the low-pressure pump is controlled as a function of the currently required fuel quantity determined by sensors and a control device. A constant lubrication flow quantity, which is essentially independent of the pressure on the delivery side, is branched off from the delivery flow of the low-pressure pump and a residual remainder flow is delivered to the intake side of the high-pressure pump.

What is claimed is:  
     
       1. A process for generating and delivering high-pressure fuel to a high-pressure storage chamber of a fuel injection system of an internal combustion engine, which comprises delivering fuel from a tank via a low pressure pump as a pre-feed pump to an intake side of a high-pressure pump, delivering a part of the fuel delivered by the low-pressure pump to the high pressure pump to lubricate the high-pressure pump, controlling the delivery quantity of the low-pressure pump or the delivery pressure on the delivery side of the low-pressure pump as a function of a currently required fuel quantity determined by sensors and a control device, and branching off from the delivery flow of the low-pressure pump a constant lubrication flow quantity, which is essentially independent of the pressure on the delivery side, and delivering a residual remainder flow of the fuel to the intake side of the high-pressure pump. 
     
     
       2. A system for generating high fuel pressure in a common rail of a fuel injection system of an internal combustion engine, comprising a low-pressure pump ( 6 ) that aspirates fuel from a tank ( 2 ), a high-pressure pump ( 14 ) that is fed by the low-pressure pump ( 6 ) and feeds fuel into a high-pressure storage chamber, and a lubricating circuit that uses the fuel, which is to be delivered, as a lubricant for lubricating the high-pressure pump ( 14 ), in which the low-pressure pump ( 6 ) is volume flow controlled by a control device ( 20 ) with which a volume flow that corresponds to a currently required fuel quantity adjusted in the low-pressure pump ( 6 ), and a delivery side ( 8 ) of the low pressure pump ( 6 ) communicates with a flow regulating valve ( 10 ) that leads to the lubrication circuit of the high-pressure pump and parallel to the flow regulating valve communicates with the intake side ( 12 ) of the high-pressure pump ( 14 ). 
     
     
       3. The system according to claim  2 , in which the low-pressure pump ( 6 ) is an electric fuel pump that includes a speed control means. 
     
     
       4. The system according to claim  3 , in which a speed sensor ( 22 ) that is associated with the speed-controlled electric fuel pump cooperates as a feedback with the control device ( 20 ) so that a speed regulation of the electric fuel pump is achieved. 
     
     
       5. A system for generating high fuel pressure in a common rail of a fuel injection system of an internal combustion engine, comprising a low-pressure pump ( 6 ′) that aspirates fuel from a tank ( 2 ), a high-pressure pump ( 14 ) that is fed by the low-pressure pump ( 6 ) and feeds fuel into a high-pressure storage chamber, and a lubricating circuit that uses the fuel which is delivered as a lubricant for lubricating the high-pressure pump ( 14 ), and a delivery pressure on the delivery side of the low-pressure pump ( 6 ′) is controlled by a control device ( 20 ) as a function of a currently required fuel quantity, and that the delivery side of the low-pressure pump ( 6 ′) communicates with a flow regulating valve ( 10 ) that leads to the lubrication circuit of the high-pressure pump ( 14 ) and parallel to the lubrication circuit of the high-pressure pump ( 14 ) communicates with the intake side ( 12 ) of the high-pressure pump ( 14 ). 
     
     
       6. The system according to claim  5 , in which the low-pressure pump ( 6 ′) is pressure regulated and controlled by the control device ( 20 ). 
     
     
       7. The system according to claim  5 , in which the low-pressure pump ( 6 ′) is constituted by a gear pump with a subsequently connected variable throttle device that is controlled by the control unit ( 20 ). 
     
     
       8. The system according to claim  7 , in which the subsequently connected variable throttle device is a throttle slide valve. 
     
     
       9. The system according to claim  7 , in which the subsequently connected variable throttle device is a synchronized solenoid valve ( 32 ) that is controlled by the control device ( 20 ) and is provided in a branch line ( 30 ) that leads back to the tank ( 2 ). 
     
     
       10. The system according to claim  2 , which includes a safety valve ( 26 ) on the delivery side of the low-pressure pump ( 6 ,  6 ′), which interrupts the fuel delivery to the high-pressure pump ( 14 ) when the pressure falls below a predetermined level. 
     
     
       11. The system according to claim  3 , which includes a safety valve ( 26 ) on the delivery side of the low-pressure pump ( 6 ,  6 ′), which interrupts the fuel delivery to the high-pressure pump ( 14 ) when the pressure falls below a predetermined level. 
     
     
       12. The system according to claim  4 , which includes a safety valve ( 26 ) on the delivery side of the low-pressure pump ( 6 ,  6 ′), which interrupts the fuel delivery to the high-pressure pump ( 14 ) when the pressure falls below a predetermined level. 
     
     
       13. The system according to claim  5 , which includes a safety valve ( 26 ) on the delivery side of the low-pressure pump ( 6 ,  6 ′), which interrupts the fuel delivery to the high-pressure pump ( 14 ) when the pressure falls below a predetermined level. 
     
     
       14. The system according to claim  6 , which includes a safety valve ( 26 ) on the delivery side of the low-pressure pump ( 6 ,  6 ′), which interrupts the fuel delivery to the high-pressure pump ( 14 ) when the pressure falls below a predetermined level. 
     
     
       15. The system according to claim  7 , which includes a safety valve ( 26 ) on the delivery side of the low-pressure pump ( 6 ,  6 ′), which interrupts the fuel delivery to the high-pressure pump ( 14 ) when the pressure falls below a predetermined level. 
     
     
       16. The system according to claim  8 , which includes a safety valve ( 26 ) on the delivery side of the low-pressure pump ( 6 ,  6 ′), which interrupts the fuel delivery to the high-pressure pump ( 14 ) when the pressure falls below a predetermined level.